1. Field of the Invention
The present invention relates to a diapause hormone, novel polypeptide, derived from Subaesophageal ganglia of a silkworm (Bombyx mori) pupa and the first thoracic ganglia of a silkworm (Bombyx mori) pupa. This polypeptide has comprises 24 amino acid residues designated by the following amino acid sequence: ##STR2## wherein X is Cys (SEQ ID NO: 1) or Trp (SEQ ID NO: 2) and R is OH or NH.sub.2.
2. Description of the Prior Art
Many species of insects diapause. There are two main hormonal mechanisms of the diapause; (1) lack of a hormone which stimulates the growth of insects, (2) secretion of a hormone which positively causes a diapause, that is, a diapause hormone. The structure of the diapause hormone has not yet been determined, but physiological properties of the hormone have been elucidated by using a partially purified diapause hormone. As one of the properties the hormone influences the formation of silkworm's eggs at a pupal stage. It acts on an ovary and specifically raises activity of trehalase locally existing in a cytolemma. Because a blood sugar of insects is trehalose, a rise of the trehalase activity contributes to an intake of a blood sugar into an ovary, resulting in accumulation and storage of carbohydrate, especially glycogen, in silkworm's eggs. In these nutritious eggs, sorbitol is synthesized from the glycogen at an embryo stage on the first day after a fertilization. The eggs enter diapause by the accumulation of sorbitol. That is to say, a large amount of sorbitol extremely decreases free water in a living body, and all reactions in the living body stop, whereby the living body is kept stable.
The structures of insect hormones, e.g., ecdysteroids, juvenile hormone, prothoracicotropic hormone, adipokinetic hormone, etc. have already been reported, wherein prothoracicotropic hormone and adipokinetic hormone are polypeptides.
The diapause hormone, secretory polypeptide, has not been isolated, purified, and sequenced prior to this invention.